Eletrodeposição de revestimentos de níquel e avaliação no desempenho eletrocatalítico para reações de evolução de hidrogênio

Abstract

In the midst of the global energy crisis and considering that its energy matrix is ​​ composed mostly of fossil fuels, which in turn contribute to CO2 emissions into the atmosphere, there was a need to seek new energy sources that could replace them without losing their efficiency. In this scenario, it was found that hydrogen has been presented as the best alternative, since hydrogen fuel is considered a clean energy source and has high energy efficiency due to its water electrolysis. However, obtaining hydrogen cleanly requires a process that is efficiently limited due to the Oxygen Evolution Reaction (OER), since water electrolysis is a kinetically slow process that has a high energy consumption and requires electrocatalysts that can reduce this consumption. Thus, the present work aims to seek the development of these electrocatalysts that are efficient and have a high cost-benefit. In this context, the studies of Ni electrodeposition on Cu through a deep eutectic solvent (DES) based on choline chloride (ChCl), composed of ChCl and ethylene glycol (EG), in the molar ratio 1ChCl:2EG, will be investigated. Thus, the techniques of cyclic voltammetry (CV), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) were used, and the crystallographic structures were analyzed by the X-ray diffraction (XRD) and linear polarization techniques. The CV results showed that the DES demonstrated a working range between -0.3 V and approximately -0.9 V. The increase in temperature caused an increase in the current signal, characteristic of the reduction of Ch+ ions. The voltammograms obtained for nickel showed that the increase in temperature resulted in an increase in the reduction current, which resulted in a higher deposition kinetics for the temperature of 80 °C. The potential required for the reduction of nickel was reduced due to the supply of thermal energy caused by the increase in temperature. The SEM results showed that there was a reduction of Ni films with nodular morphology that grow as the temperature increases, the EDS showed the presence of the chemical element Ni and the XRD showed that the physical characteristic formed by the deposition of Ni on Cu presents a face-centered cubic crystalline structure. The polarization curves showed that all parameters acquired the same profile, but the most catalytic coatings were Ni80 and Ni60, in this order, classified as ideal